Among the several noise-generation mechanisms of airfoil self-noise, trailing-edge bluntness noise is an important source, which caused by vortex shedding at blunt trailing edges. A numerical study on control using bio-inspired wavy leading edges presented in this paper. The high-fidelity, improved, delayed, detached eddy simulation (IDDES) method was used to calculate flow field, and acoustic ...

The present paper is a state-of-the-art of a special class of analytical models to predict the broadband noise generated by thin airfoils in a flow, either clean or disturbed. Three generating mechanisms are addressed, namely the noise from the impingement of upstream turbulence called turbulence-interaction noise, the noise due to the scattering of boundary-layer turbulence as sound at the tra...

Airfoils operating at low-to-moderate Reynolds number may produce noise that contains one or more high amplitude tonal components. Many previous researchers have attributed airfoil tonal noise to a feedback loop between instabilities in the laminar boundary layer and the acoustic waves produced at the trailing edge. There is, however, limited experimental evidence to verify this proposed hypoth...

Direct numerical simulations of a turbulent boundary layer over a bump were performed to examine the effects of surface longitudinal curvature on wall pressure fluctuations (pw) and flow induced noise. Turbulence statistics and frequency spectra were obtained to elucidate the response of wall pressure fluctuations to the longitudinal curvature and to the corresponding pressure gradient. Wall pr...

This paper treats the problem of recovering sustainable nondescending (safe) flight in a transport aircraft after one or more of its control effectors fail. Such recovery can be a challenging goal for many transport aircraft currently in the operational fleet for two reasons. First, they have very little redundancy in their means of generating control forces and moments. These aircraft have, as...

A new process for concurrent trim and structural optimization of Active Aeroelastic Wing technology is presented. The new process treats trim optimization and structural optimization as integrated problems in the same mathematical formulation, in which control surface gear ratios are added as design variables to a standard structural optimization algorithm. This new approach is in contrast to m...

We present a numerical method for the dynamics of a flexible body in an inviscid flow with a free vortex sheet. The formulation is implicit with respect to body variables and explicit with respect to the free vortex sheet. We apply the method to a flexible foil driven periodically in a steady stream. We give numerical evidence that the method is stable and accurate for a relatively small comput...

This paper addresses the feasibility of using trailing edge flaps to reconfigure a helicopter rotor blade following a failure of the pitch link, which makes the blade freefloating in pitch and otherwise uncontrollable. A coupled rotor-fuselage model is developed which allowed for rotor anisotropy. A new, optimization-based, trim procedure is developed to determine the dynamics of the failed bla...